1. Field of the Invention
The present invention relates to a semiconductor device that has a photovoltaic element.
2. Description of the Related Art
There are many known photovoltaic devices used in the detection of electromagnetic waves, in general, for example, an object, generally called a light sensor, that is sensitive to light from the ultraviolet region to the infrared region of the electromagnetic spectrum. Out of these light sensors, one that has sensitivity in the visible light region, wavelength in the range from 400 nm to 700 nm, is called a visible light sensor, in particular, and visible light sensors are being used in many different kinds of devices for brightness adjustment, on/off control, and the like that are needed in a person's living environment.
In particular, in a display device, the brightness of ambient light around the display device is detected, and the luminance of the display is adjusted. Because the brightness of ambient light is detected, optimal luminance for the display can be obtained, and accordingly, the amount of electric power that is wasted can be reduced. These kinds of light sensors, which are used to adjust the luminance of a display, are used, for example, in cellular phones and personal computers.
Moreover, not only is the brightness of ambient light detected, the luminance of the display device and a backlight of a liquid crystal display device, in particular, is detected by a light sensor, and the luminance of the display screen is adjusted, as well.
In this kind of light sensor, a photodiode is used in a sensing portion, and the output current of the photodiode is amplified by an amplifier circuit. For this kind of amplifier circuit, a current mirror circuit, for example, is used (for an example, refer to Patent Reference Document 1).
Furthermore, in this kind of semiconductor integrated circuit, there are problems caused by static electricity generated while the semiconductor integrated circuit is being manufactured or being used in that the electrode and the semiconductor element are damaged and the reliability of the semiconductor element is decreased. In order to prevent damage due to electrostatic discharge from occurring in the semiconductor element and the electrode, a protective circuit connected to the terminal is fabricated along with the semiconductor element, and a high electric potential generated in the terminal is prevented from being applied to the semiconductor element by the protective circuit.
Patent Reference Document 1: Japanese Patent No. 3444093